Re: [PATCH 3/3] pids: Make it possible to clone tasks with given pids

From: Pavel Emelyanov <xemul@parallels.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Alan Cox <alan@linux.intel.com>,
	Roland McGrath <roland@hack.frob.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Tejun Heo <tj@kernel.org>, Cyrill Gorcunov <gorcunov@openvz.org>,
	James Bottomley <jbottomley@parallels.com>
Subject: Re: [PATCH 3/3] pids: Make it possible to clone tasks with given pids
Date: Fri, 18 Nov 2011 14:05:43 +0400	[thread overview]
Message-ID: <4EC62DF7.6000805@parallels.com> (raw)
In-Reply-To: <20111117183605.GA20552@redhat.com>

On 11/17/2011 10:36 PM, Oleg Nesterov wrote:
> My previous objection was wrong, I should try to find something else ;)
> 
> On 11/17, Pavel Emelyanov wrote:
>>
>> +static int set_pidmap(struct pid_namespace *pid_ns, int pid)
>> +{
>> +	int offset;
>> +	struct pidmap *map;
>> +
>> +	/*
>> +	 * When creating a new pid namespace we must make its init
>> +	 * have pid == 1 in it.
>> +	 */
>> +	if (pid_ns->child_reaper == NULL)
>> +		return 0;
>> +
>> +	/*
>> +	 * Don't allow to create a task with a pid which has recently
>> +	 * belonged to some other (dead already) task. Only init (of
>> +	 * a freshly created namespace) and his clones can do this.
>> +	 */
>> +	if (pid_ns->last_pid != 1)
>> +		return -EPERM;
>> +
>> +	map = &pid_ns->pidmap[pid/BITS_PER_PAGE];
> 
> probably we should check that map < PIDMAP_ENTRIES ?

Yes, you're right here. The checks for given pid being correct are required. Will fix.

> Oleg.

Thanks,
Pavel